Safety helmet

ABSTRACT

A safety helmet is described which includes means to allow the impact status or history of the helmet to be determined. The means may comprise an electrical sensor or alternatively may be arranged to provide a visible indication in the event of an impact.

This invention relates to a safety helmet.

Safety helmets are commonly worn by, for example, horse riders, cyclistsand motor cyclists, with the aim of reducing injury to the wearer's headin the event that he falls, crashes or, for horse riders, is thrown.Safety helmets are also commonly worn when participating in certainother sports or activities. A typical safety helmet design incorporatesa layer or pieces of a compressible or deformable material located suchthat, in the event of the wearer's head impacting upon an object, or anobject hitting the helmet, the compressible or deformable material willdeform to absorb at least some of the impact forces thereby lesseningthe risk of injury to the wearer. As the deformation of the compressibleor deformable material can be permanent, it is usually recommended thatafter such an impact has occurred, the helmet is disposed of as itsability to absorb future impact forces may be reduced. Alternatively,the helmet may be repaired.

Although disposal or repair is recommended, there are often situationswhere the wearer may consider the impact to be of insufficient severityto require the helmet to be replaced or repaired, and so a helmet may beused which is not capable of serving its intended purpose. There arealso situations where helmets are shared or used by a number ofindividuals none of whom may know whether an impact has occurred whilstthe helmet was being used by another. It is an object of the inventionto provide a helmet user with the ability to determine the impacthistory or impact status of a helmet. One way of achieving this is toprovide a mechanism whereby a record can be kept of the impactsexperienced by a helmet.

According to one aspect of the invention there is provided a helmetcomprising an impact sensor and a memory arranged to store impact datafrom the impact sensor.

It will be appreciated that by appropriate interrogation of the memory,a user can determine whether or not the helmet has been involved in animpact of magnitude sufficient to impair the subsequent performancethereof.

The memory may be arranged to store the impact information in a range ofways. For example, it may record the time and magnitude of each impactexperienced by the helmet. Alternatively, some form of filtering may beapplied so that only data representative of impacts exceeding apre-determined threshold value are recorded. Although the time of the oreach impact may be recorded, there may be occasions when thisinformation is not required and so this data may not be stored. In asimple embodiment, the memory may be bistable and arranged to switchbetween a first, normal, state and a second, warning, state upon theoccurrence of an impact or series of impacts greater than apre-determined value.

The helmet may further include a warning device adapted to be controlledusing the data stored in the memory.

For example, a warning may be triggered in the event that an impact issensed the magnitude of which is greater than a predetermined threshold.

The predetermined threshold may be set by, for example, the helmetmanufacturer, so as to be tailored to, for example, the helmet designand the intended use thereof.

The warning preferably comprises a visible warning, for example anappropriately controlled liquid crystal display. Alternatively, awarning light, for example an LED arranged to be illuminated in theevent of the occurrence of a large impact, may be provided. However,other warnings could be used. For example, a light may be switched offin the event of an impact, rendering the helmet fail-safe. Anotherpossibility is to provide an audible warning.

The impact sensor may take a range of forms. In one arrangement itcomprises a layer of a material sensitive to the occurrence of animpact.

The said layer of material may be incorporated into the helmet butcould, alternatively, be retrofitted thereto, if desired. Where intendedto be retrofitted, the layer may be fitted by, a manufacturer orrepairer. Alternatively, a suitable kit may be supplied to allow theuser to fit the layer to the helmet.

The layer of material conveniently comprises a layer of quantumtunnelling composite material. The electrical insulating/conductingproperties of such a material vary when the material is pressed,squashed, twisted or stretched thus by measuring the electricalresistance across the layer, a measurement of whether or not an impactis occurring and the magnitude of any such impact can be made. Thematerial may be in sheet form or alternatively may comprise granulesmixed with and incorporated into the material of part of the helmet. Thelayer is preferably continuous, but could alternatively bediscontinuous, for example in the form of a plurality of isolatedregions or pads.

Although the sensor may take the above described form, it will beappreciated that this need not be the case and a range of other sensorscould be used.

For example, the sensor could be capacitance based. In such anarrangement, a pair of electrically conductive layers are separated byan electrically insulating material. In the event of an impact, theelectrically insulating material will deform, allowing the electricallyconductive layers to be forced closer to one another thereby changingthe capacitance therebetween. A plurality of discrete, self-containedsensor capacitors may be used instead of a single, larger sensorcapacitor, if desired. Other possibilities, include the use of piezoelectric materials, the application of a force to which results in ameasurable change in the electrical properties thereof. Other forms ofstrain gauge could also be used.

Although the provision of a suitable sensor and memory allows a user, byappropriate interrogation of the memory, to ascertain informationrelating to impacts experienced by a helmet and thus determine whetheror not he considers it to be safe for use, it will be appreciated thatother techniques are possible.

In accordance with another aspect of the invention, therefore, there isprovided a helmet, and means associated with the helmet capable ofproviding an indication of the impact status or history of the helmet.

The means may take the form of a sensor and memory as describedhereinbefore. Alternatively, the means capable of providing anindication could comprise a component the state of which will change inthe event of an impact exceeding a pre-determined threshold, the stateof the component being apparent to a user of the helmet. By way ofexample, the component may be arranged to change colour in the event ofa large impact, the change of colour providing an indication to a userthat the helmet has been involved in an impact. Alternatively, thecomponent may be designed to break, crack, shatter or otherwise deformin the event of an impact in such a manner as to provide an indicationthat an impact has occurred. Preferably the component is encased, forexample within or behind a suitable transparent material layer, so as tobe contained but visible to a user. Another possibility is to provideone or more reservoirs containing an ink or dye in the helmet, thereservoirs being arranged to rupture, break, leak or overflow in theevent of an impact, the escaped ink or dye providing an indication to auser of the helmet's involvement in an impact.

The invention will further be described, by way of example, withreference to the accompanying drawings, in which:

FIGS. 1 and 2 are views illustrating helmets in accordance withembodiments of the invention.

FIG. 1 illustrates a helmet of the type commonly worn by motor cyclistswhich comprises an outer shell 10, an impact absorbing layer 12 and aninner liner 14. Between the liner 14 and the layer 12 is a layer 16 of acompressible material intended to improve the fit of the helmet on thewearer and to improve comfort. Although a range of different materialsmay be used in the helmet, the shell 10 is typically of a plasticsmaterial, for example a fibre reinforced plastics material. The impactabsorbing layer 12 is typically of a cellular material, for example afoamed plastics material. The layer 16 may be of urethane foam.

When the wearer of the helmet experiences an impact which, in theabsence of the helmet would be an impact to the head, the impactabsorbing layer 12 deforms, thereby absorbing at least some of theimpact force and reducing the risk of injury to the wearer.

In accordance with the invention, in order to allow monitoring of theoccurrence of such impacts, an impact sensor in the form of a layer 18of a material sensitive to the occurrence of such impacts is provided.In the arrangement illustrated the layer 18 is located between the outershell 10 and the impact absorbing layer 12. It will be appreciated,however, that the layer may be provided elsewhere, for example on theoutside of the outer shell 10.

The layer 18 is formed from a so-called quantum tunnelling compositematerial. Such a material has the quality that its electrical resistancevaries as the mechanical load applied thereto varies. The electricalresistance across the layer 18 is, under normal circumstances, high.However, in the event of an impact resulting from, for example, thewearer being involved in a road traffic accident and his head impactingupon the road surface or another hard object, the impact force willtemporarily squash or compress the layer 18 thus causing a temporaryreduction in the electrical resistance across the layer 18.

The top, rear part of the helmet is shaped to define a projection 20adapted to house a monitoring unit 22. The unit 22 is an electronic unitarranged to monitor the electrical resistance across the layer 18. Thismay be achieved by providing electrically conductive layers on eachmajor surface of the layer 18, the conductive layers being isolated fromone another by the layer 18, and by providing electrical connectionsbetween the unit 22 and the conductive layers, the unit 22 monitoringthe electrical resistance between the connections using any suitablecircuitry. The unit 22 includes a storage device or memory which is usedto store data representative of the measured resistance values, andhence of the impact state of the helmet, over time. It will beappreciated, therefore, that by appropriate interrogation of the storagedevice, a history of events or impacts experienced by the helmet can bederived. Such interrogation may be achieved by connecting a suitabledevice to the unit 22 to download data from the storage device.

In addition to storage of the resistance data, the unit 22 is arrangedto compare the resistance data with a stored threshold value todetermine whether or not an impact has occurred of a magnitudesufficient to render the helmet unsuitable for further use. The storedthreshold value may be set by the helmet manufacturer and will depend,to some extent, upon the helmet design and the intended use thereof. Inthe event that the comparison of the resistance data with the storedthreshold indicates that the helmet has experienced an impact greatenough to render the helmet unsuitable for further use, a warning istriggered. In the illustrated arrangement, the warning takes the form ofa display device 24 in the form of a liquid crystal display which iscontrolled to display a suitable message. As illustrated, the device 24is located so as to define part of the wall of the projection 20 so asto be clearly visible. Alternatively, the warning could make use of awarning light in the form of a LED operable in the event that an impacthas occurred.

The unit 22 conveniently includes an internal power source in the formof, for example, a battery. Obviously, where a warning light is used,there is the risk that if the battery runs flat, no warning signal isproduced. It may be preferred to operate on a failsafe system wherebythe impact warning is triggered by, for example, switching off (ratherthan on) a warning light. In the event of a flat battery, no warninglight would be illuminated, and so no impression that the helmet is safewould be given. A similar operating technique may be used where thewarning is displayed on a liquid crystal display.

Further possibilities include arranging for the warning light or displayto be illuminated or operated only when, for example, a test button ispressed. With such an arrangement, a user could test the helmet beforeuse and note whether or not a warning indicative of the impact state ofthe helmet is produced. Further, it may be possible to provide anaudible warning instead of or in addition to the visible warning.

In the arrangement described hereinbefore, the layer 18 is a separatelayer. However, this need not be the case. Quantum tunnelling compositematerials are available in granular form which can be incorporated intoother materials. For example, the material may be incorporated into theplastics material of the outer shell 10, if desired. Further, in thearrangement described hereinbefore the layer 18 is continuous, providinginformation relating to the occurrence of impacts on any part of thehelmet. However, provided a reduction in the sensitivity of the systemis acceptable, the layer 18 may be discontinuous or may comprise anumber of separate sensor regions or “pads”.

A further alternative arrangement is shown in FIG. 2. In thisarrangement, a helmet of conventional form having a shell 10 and layer12 is modified by the fitting thereof of a layer 18 of quantumtunnelling material and a housing 20 containing a monitoring unit 22 andwarning device 24. The layer 18, unit 22 and device 24 may bepermanently or semi-permanently secured in position using any suitabletechnique, for example by a suitable adhesive, or may be removablysecured to the helmet, for example using a drawstring, and operate asdescribed hereinbefore to allow monitoring of impacts experienced by thehelmet.

The helmet impact monitoring techniques described hereinbefore make useof electronic sensors and memory units, for example using solid statecomponents. It will be appreciated that a number of other electricallyoperated sensor techniques could be used. For example, piezo electriccomponents could be mounted upon the helmet and arranged to act like astrain gauge. In the event of an impact, the electrical properties ofthe components would change and this could be used to indicate that animpact has occurred. Other types of strain gauge could be used.

Another possibility is to use one or more capacitors to sense theoccurrence of an impact. By way of example, one or more sensor regionsof the helmet may be provided with a pair of spaced electricallyconductive layers, an electrical insulator being located between theconductive layers. In the event of an impact, the layers will be forcedcloser together, the insulator deforming to allow such movement, with aconsequent change in the capacitance between the conductive layers. Thecapacitors may take the form of fairly small, discrete, self-containedcomponents, if desired. Although the capacitance may be continuouslymonitored and readings stored in a memory, the device may be arranged tobe inactive whilst in use, and arranged to be connected, periodically,to a reader unit arranged to determine the measured capacitance andthereby determine whether or not the helmet is safe for use.

It will be appreciated that there is a wide range of other possible waysof enabling a user to determine whether or not a helmet has beeninvolved in an impact which could impair the impact absorbing propertiesthereof. For example, a number of ink or dye containing packets or cellsmay be incorporated into the helmet and arranged to rupture to allow theink or dye to bleed therefrom in the event of a large impact. The ink ordye would then provide an indication to a user that the helmet has beeninvolved in an impact. The packets or cells could be provided at orclose to the surface of the helmet or located within, for example, theshock absorbing layer thereof. Where not located at the surface of thehelmet, it may be desirable to incorporate, for example, a wickingmaterial to allow passage of the ink or dye to a location in which itcan be viewed. If desired, a transparent element may be provided in thehelmet to allow inspection to determine whether or not the helmet issafe for use.

Alternatively, a component may be incorporated into the helmet, thecomponent being adapted to change state in the event of an impact, thestate of the component providing an indication to the user of whether ornot the helmet has been involved in an impact. By way of example, thecomponent may be of a material arranged to break, shatter, crack orotherwise deform in a noticeable manner in the event of an impact.Alternatively, the component may be arranged to undergo a change ofcolour in the event of an impact. In such an arrangement, it may bedesirable to encase or enclose the component, for example within orbeneath a layer of a transparent material.

As with the electronic arrangements, the components which enable impactinformation presentation may be incorporated upon initial manufacture ormay be subsequently added to the helmet, either by a manufacturer or bythe use of, for example, a kit of components.

Although the description hereinbefore is primarily of a helmet intendedfor use in motor cycling, it will be appreciated that the invention maybe incorporated into helmets intended for use in a wide variety ofapplications, such a horse riding, cycling, motor racing or otherapplications in which helmets are worn to reduce the risk of headinjury.

1. A helmet comprising a shock absorbing element and means associated therewith to provide an indication of the impact status or history of the helmet.
 2. A helmet according to claim 1, wherein the said means comprises an electrical impact sensor.
 3. A helmet according to claim 2, wherein the electrical impact sensor comprises at least one capacitor, the electrical capacitance of which changes in the event of an impact.
 4. A helmet according to claim 2, wherein the electrical impact sensor comprises a strain gauge sensitive to the occurrence of an impact.
 5. A helmet according to claim 4, wherein the strain gauge incorporates a piezo electric component.
 6. A helmet according to claim 2, wherein the electrical impact sensor comprises a quantum tunnelling material, and monitoring means arranged to monitor the electrical properties of the quantum tunnelling material.
 7. A helmet according to claim 2, further comprising a memory arranged to record data representative of the occurrence of impacts.
 8. A helmet according to claim 2, further comprising a monitoring unit arranged to monitor the output of the impact sensor.
 9. A helmet according to claim 8, wherein the monitoring unit is connected to the impact sensor periodically.
 10. A helmet according to claim 2, further comprising a warning device arranged to trigger a warning in the event that the impact sensor has detected the occurrence of an impact of magnitude greater than a predetermined magnitude.
 11. A helmet according to claim 1, wherein the said means comprises a component the state of which changes in the event of an impact exceeding a predetermined threshold, the state of the component being apparent to a user of the helmet.
 12. A helmet according to claim 11, wherein the change in state of the component is visibly apparent.
 13. A helmet according to claim 12, wherein the helmet includes a transparent element to allow the state of the component to be determined.
 14. A helmet according to claim 12, wherein the colour of the component changes in the event of an impact.
 15. A helmet according to claim 12, wherein the component is arranged to break, crack, shatter or otherwise visibly deform in the event of an impact.
 16. A helmet according to claim 12, wherein the component includes at least one rupturable ink or dye reservoir arranged to rupture, break, leak or overflow in the event of an impact.
 17. (canceled) 